My current conclusions are that the differences in negative apparent sharpness is very clear BUT DEPENDS on the film being used. I see more differences in apparent sharpness using Efke PL100 than Fortepan 200 for example.
You are right that it really depends on the type of scene being shot. I find that my negatives of high key scenes (where EVs are in the double digits, e.g. EV range 11-14 or 14-17 etc., as opposed to EV ranges 7-10 or 5-8) are better suited for minimal agitation. It is when printing these negatives that the apparent sharpness comes across on paper as well (and yes it is the micro contrast that kicks a#*¤ - recall that scene I posted with the bark detail and fallen branch in snow). Yes, your conclusion matches what I have observed about subjects with a lot of adjacent highlight and shadow areas. They print better.
The question about whether it is worth the trouble (more time, more solution) is hard to determine right now. The best advise I can give myself is to choose wisely which negatives should be given the minimal agitation treatment and even prior to that making the correct film choice for the particular scene being recorded. I believe that there was an article in the Unblinking Eye concerning film choices based on scene contrast. It certainly applies here.
Despite some disappointing prints, I am still continuing with the experiment and in fact I have been making slight modifications to the agitation procedures. At the very least I am learning more about the films I use and how they react to Pyrocat HD. So I guess it is worth it after all!